My DS just turned 2. He doesn't speak apart from a few words that can be hard to understand. He's not badly behaved but is just very, very stubborn and doesn't respond to instructions or prompts in any way. It's like he's just not interested in engaging with the outside world at all unless it's on his terms exactly. He likes to be read to and taken for walks but he's not particularly interested in involving other people in his play and will happily concentrate for hours alone with his toys. I get that he's a 2-year-old but sometimes I wonder whether his resistance to things is a bit extreme - any attempt to move him onto something else or remove something he's looking at will cause a loud protest.
I wouldn't say we're 'gentle parents' in the popular sense as we use the word 'no' and aren't afraid to set boundaries. Because of this I think his tantrums have calmed down significantly in the past few months.
We have ASD in the family, but to be honest he doesn't really present that way to me. He's always been a great sleeper, his eating is pretty good and he doesn't seem particularly sensitive to noise, environment, etc. He's also apparently quite sociable at nursery and has a lot of friends, and the staff say he's really good with the babies and likes to pat them on the head and tries to help feed them. Sometimes when we're out and about we'll see children from nursery and they will excitedly shout his name, so I think he must be having meaningful interactions even though he doesn't talk. I think he understands everything we say as he points to pictures in books when we say the words.
As a baby he never rolled over or crawled, though he sat up, stood and walked at fairly normal ages. His younger sibling is the same, though I made a point of lying them down/sitting them on the floor constantly so they were free to move as much as they wanted. When I've been to baby groups I can't help thinking that other babies move quite differently to them - other babies just seem so much more flexible and bendy and like they're happy to experiment with moving around, whilst mine were very watchful and happy to sit still. My DS didn't move around at all (or show any wish to!) until he was about a year old and started scooting along the furniture.
Apologies if I haven't explained properly or if I later add details I've forgotten to put here. Please be kind!